The tracker dog was helpful in finding the fugitive.

Police dogs are very effective in tracking criminals.

He is an excellent tracker and never gets lost in the forest.

He is a famous author and a person who is respected by many people.

The criminal was arrested by the police.

This medicine is very effective.

The effectiveness of this medicine has been scientifically proven.

The police started chasing the criminal.

The police are chasing the criminal.

I was amazed at his extraordinary talent.